/*
Copyright 2017 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package vfs

import (
	"bytes"
	"crypto/tls"
	"encoding/hex"
	"fmt"
	"io"
	"net/http"
	"os"
	"path"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"github.com/go-ini/ini"
	"github.com/gophercloud/gophercloud"
	"github.com/gophercloud/gophercloud/openstack"
	swiftcontainer "github.com/gophercloud/gophercloud/openstack/objectstorage/v1/containers"
	swiftobject "github.com/gophercloud/gophercloud/openstack/objectstorage/v1/objects"
	"github.com/gophercloud/gophercloud/pagination"
	"k8s.io/apimachinery/pkg/util/wait"
	"k8s.io/client-go/util/homedir"
	"k8s.io/klog"
	"k8s.io/kops/util/pkg/hashing"
)

func NewSwiftClient() (*gophercloud.ServiceClient, error) {
	config := OpenstackConfig{}

	// Check if env credentials are valid first
	authOption, err := config.GetCredential()
	if err != nil {
		return nil, err
	}

	pc, err := openstack.NewClient(authOption.IdentityEndpoint)
	if err != nil {
		return nil, fmt.Errorf("error building openstack provider client: %v", err)
	}

	tlsconfig := &tls.Config{}
	tlsconfig.InsecureSkipVerify = true
	transport := &http.Transport{TLSClientConfig: tlsconfig}
	pc.HTTPClient = http.Client{
		Transport: transport,
	}

	klog.V(2).Info("authenticating to keystone")

	err = openstack.Authenticate(pc, authOption)
	if err != nil {
		return nil, fmt.Errorf("error building openstack authenticated client: %v", err)
	}

	var endpointOpt gophercloud.EndpointOpts
	if region, err := config.GetRegion(); err != nil {
		klog.Warningf("Retrieving swift configuration from openstack config file: %v", err)
		endpointOpt, err = config.GetServiceConfig("Swift")
		if err != nil {
			return nil, err
		}
	} else {
		endpointOpt = gophercloud.EndpointOpts{
			Type:   "object-store",
			Region: region,
		}
	}

	client, err := openstack.NewObjectStorageV1(pc, endpointOpt)
	if err != nil {
		return nil, fmt.Errorf("error building swift client: %v", err)
	}
	return client, nil
}

type OpenstackConfig struct {
}

func (_ OpenstackConfig) filename() (string, error) {
	name := os.Getenv("OPENSTACK_CREDENTIAL_FILE")
	if name != "" {
		klog.V(2).Infof("using openstack config found in $OPENSTACK_CREDENTIAL_FILE: %s", name)
		return name, nil
	}

	homeDir := homedir.HomeDir()
	if homeDir == "" {
		return "", fmt.Errorf("can not find home directory")
	}
	f := filepath.Join(homeDir, ".openstack", "config")
	klog.V(2).Infof("using openstack config found in %s", f)
	return f, nil
}

func (oc OpenstackConfig) getSection(name string, items []string) (map[string]string, error) {
	filename, err := oc.filename()
	if err != nil {
		return nil, err
	}
	config, err := ini.Load(filename)
	if err != nil {
		return nil, fmt.Errorf("error loading config file: %v", err)
	}
	section, err := config.GetSection(name)
	if err != nil {
		return nil, fmt.Errorf("error getting section of %s: %v", name, err)
	}
	values := make(map[string]string)
	for _, item := range items {
		values[item] = section.Key(item).String()
	}
	return values, nil
}

func (oc OpenstackConfig) GetCredential() (gophercloud.AuthOptions, error) {

	// prioritize environment config
	env, enverr := openstack.AuthOptionsFromEnv()
	if enverr != nil {
		klog.Warningf("Could not initialize swift from environment: %v", enverr)
		// fallback to config file
		return oc.getCredentialFromFile()
	}
	return env, nil

}

func (oc OpenstackConfig) GetRegion() (string, error) {

	var region string
	if region = os.Getenv("OS_REGION_NAME"); region != "" {
		if len(region) > 1 {
			if region[0] == '\'' && region[len(region)-1] == '\'' {
				region = region[1 : len(region)-1]
			}
		}
		return region, nil
	}

	items := []string{"region"}
	// TODO: Unsure if this is the correct section for region
	values, err := oc.getSection("Global", items)
	if err != nil {
		return "", fmt.Errorf("Region not provided in OS_REGION_NAME or openstack config section GLOBAL")
	}
	return values["region"], nil
}

func (oc OpenstackConfig) getCredentialFromFile() (gophercloud.AuthOptions, error) {
	opt := gophercloud.AuthOptions{}
	name := "Default"
	items := []string{"identity", "user", "user_id", "password", "domain_id", "domain_name", "tenant_id", "tenant_name"}
	values, err := oc.getSection(name, items)
	if err != nil {
		return opt, err
	}

	for _, c1 := range []string{"identity", "password"} {
		if values[c1] == "" {
			return opt, fmt.Errorf("missing %s in section of %s", c1, name)
		}
	}

	checkItems := [][]string{{"user", "user_id"}, {"domain_name", "domain_id"}, {"tenant_name", "tenant_id"}}
	for _, c2 := range checkItems {
		if values[c2[0]] == "" && values[c2[1]] == "" {
			return opt, fmt.Errorf("missing %s and %s in section of %s", c2[0], c2[1], name)
		}
	}

	opt.IdentityEndpoint = values["identity"]
	opt.UserID = values["user_id"]
	opt.Username = values["user"]
	opt.Password = values["password"]
	opt.TenantID = values["tenant_id"]
	opt.TenantName = values["tenant_name"]
	opt.DomainID = values["domain_id"]
	opt.DomainName = values["domain_name"]
	opt.AllowReauth = true

	return opt, nil
}

func (oc OpenstackConfig) GetServiceConfig(name string) (gophercloud.EndpointOpts, error) {
	opt := gophercloud.EndpointOpts{}
	items := []string{"service_type", "service_name", "region", "availability"}
	values, err := oc.getSection(name, items)
	if err != nil {
		return opt, err
	}

	if values["region"] == "" {
		return opt, fmt.Errorf("missing region in section of %s", name)
	}

	opt.Type = values["service_type"]
	opt.Name = values["service_name"]
	opt.Region = values["region"]
	opt.Availability = gophercloud.Availability(values["availability"])

	return opt, nil
}

// SwiftPath is a vfs path for Openstack Cloud Storage.
type SwiftPath struct {
	client *gophercloud.ServiceClient
	bucket string
	key    string
	hash   string
}

var _ Path = &SwiftPath{}
var _ HasHash = &SwiftPath{}

// swiftReadBackoff is the backoff strategy for Swift read retries.
var swiftReadBackoff = wait.Backoff{
	Duration: time.Second,
	Factor:   1.5,
	Jitter:   0.1,
	Steps:    4,
}

// swiftWriteBackoff is the backoff strategy for Swift write retries.
var swiftWriteBackoff = wait.Backoff{
	Duration: time.Second,
	Factor:   1.5,
	Jitter:   0.1,
	Steps:    5,
}

func NewSwiftPath(client *gophercloud.ServiceClient, bucket string, key string) (*SwiftPath, error) {
	bucket = strings.TrimSuffix(bucket, "/")
	key = strings.TrimPrefix(key, "/")

	return &SwiftPath{
		client: client,
		bucket: bucket,
		key:    key,
	}, nil
}

func (p *SwiftPath) Path() string {
	return "swift://" + p.bucket + "/" + p.key
}

func (p *SwiftPath) Bucket() string {
	return p.bucket
}

func (p *SwiftPath) String() string {
	return p.Path()
}

func (p *SwiftPath) Remove() error {
	done, err := RetryWithBackoff(swiftWriteBackoff, func() (bool, error) {
		opt := swiftobject.DeleteOpts{}
		_, err := swiftobject.Delete(p.client, p.bucket, p.key, opt).Extract()
		if err != nil {
			if isSwiftNotFound(err) {
				return true, os.ErrNotExist
			}
			return false, fmt.Errorf("error deleting %s: %v", p, err)
		}

		return true, nil
	})
	if err != nil {
		return err
	} else if done {
		return nil
	} else {
		return wait.ErrWaitTimeout
	}
}

func (p *SwiftPath) Join(relativePath ...string) Path {
	args := []string{p.key}
	args = append(args, relativePath...)
	joined := path.Join(args...)
	return &SwiftPath{
		client: p.client,
		bucket: p.bucket,
		key:    joined,
	}
}

func (p *SwiftPath) WriteFile(data io.ReadSeeker, acl ACL) error {
	done, err := RetryWithBackoff(swiftWriteBackoff, func() (bool, error) {
		klog.V(4).Infof("Writing file %q", p)
		if _, err := data.Seek(0, 0); err != nil {
			return false, fmt.Errorf("error seeking to start of data stream for %s: %v", p, err)
		}

		createOpts := swiftobject.CreateOpts{Content: data}
		_, err := swiftobject.Create(p.client, p.bucket, p.key, createOpts).Extract()
		if err != nil {
			return false, fmt.Errorf("error writing %s: %v", p, err)
		}

		return true, nil
	})
	if err != nil {
		return err
	} else if done {
		return nil
	} else {
		// Shouldn't happen - we always return a non-nil error with false.
		return wait.ErrWaitTimeout
	}
}

// To prevent concurrent creates on the same file while maintaining atomicity of writes,
// we take a process-wide lock during the operation.
// Not a great approach, but fine for a single process (with low concurrency).
// TODO: should we enable versioning?
var createFileLockSwift sync.Mutex

func (p *SwiftPath) CreateFile(data io.ReadSeeker, acl ACL) error {
	createFileLockSwift.Lock()
	defer createFileLockSwift.Unlock()

	// Check if exists.
	_, err := RetryWithBackoff(swiftReadBackoff, func() (bool, error) {
		klog.V(4).Infof("Getting file %q", p)

		_, err := swiftobject.Get(p.client, p.bucket, p.key, swiftobject.GetOpts{}).Extract()
		if err == nil {
			return true, nil
		} else if isSwiftNotFound(err) {
			return true, os.ErrNotExist
		} else {
			return false, fmt.Errorf("error getting %s: %v", p, err)
		}
	})
	if err == nil {
		return os.ErrExist
	} else if !os.IsNotExist(err) {
		return err
	}

	err = p.createBucket()
	if err != nil {
		return err
	}

	return p.WriteFile(data, acl)
}

func (p *SwiftPath) createBucket() error {
	done, err := RetryWithBackoff(swiftWriteBackoff, func() (bool, error) {
		_, err := swiftcontainer.Get(p.client, p.bucket, swiftcontainer.GetOpts{}).Extract()
		if err == nil {
			return true, nil
		}
		if isSwiftNotFound(err) {
			createOpts := swiftcontainer.CreateOpts{}
			_, err = swiftcontainer.Create(p.client, p.bucket, createOpts).Extract()
			return err == nil, err
		}
		return false, err
	})
	if err != nil {
		return err
	} else if done {
		return nil
	} else {
		// Shouldn't happen - we always return a non-nil error with false.
		return wait.ErrWaitTimeout
	}
}

// ReadFile implements Path::ReadFile
func (p *SwiftPath) ReadFile() ([]byte, error) {
	var b bytes.Buffer
	done, err := RetryWithBackoff(swiftReadBackoff, func() (bool, error) {
		b.Reset()
		_, err := p.WriteTo(&b)
		if err != nil {
			if os.IsNotExist(err) {
				// Not recoverable
				return true, err
			}
			return false, err
		}
		// Success!
		return true, nil
	})
	if err != nil {
		return nil, err
	} else if done {
		return b.Bytes(), nil
	} else {
		// Shouldn't happen - we always return a non-nil error with false
		return nil, wait.ErrWaitTimeout
	}
}

// WriteTo implements io.WriterTo
func (p *SwiftPath) WriteTo(out io.Writer) (int64, error) {
	klog.V(4).Infof("Reading file %q", p)

	opt := swiftobject.DownloadOpts{}
	result := swiftobject.Download(p.client, p.bucket, p.key, opt)
	if result.Err != nil {
		if isSwiftNotFound(result.Err) {
			return 0, os.ErrNotExist
		}
		return 0, fmt.Errorf("error reading %s: %v", p, result.Err)
	}
	defer result.Body.Close()

	return io.Copy(out, result.Body)
}

func (p *SwiftPath) readPath(opt swiftobject.ListOpts) ([]Path, error) {
	var ret []Path
	done, err := RetryWithBackoff(swiftReadBackoff, func() (bool, error) {
		var paths []Path
		pager := swiftobject.List(p.client, p.bucket, opt)
		err := pager.EachPage(func(page pagination.Page) (bool, error) {
			objects, err1 := swiftobject.ExtractInfo(page)
			if err1 != nil {
				return false, err1
			}
			for _, o := range objects {
				child := &SwiftPath{
					client: p.client,
					bucket: p.bucket,
					key:    o.Name,
					hash:   o.Hash,
				}
				paths = append(paths, child)
			}

			return true, nil
		})
		if err != nil {
			if isSwiftNotFound(err) {
				return true, os.ErrNotExist
			}
			return false, fmt.Errorf("error listing %s: %v", p, err)
		}
		klog.V(8).Infof("Listed files in %v: %v", p, paths)
		ret = paths
		return true, nil
	})
	if err != nil {
		return nil, err
	} else if done {
		return ret, nil
	} else {
		return nil, wait.ErrWaitTimeout
	}
}

// ReadDir implements Path::ReadDir.
func (p *SwiftPath) ReadDir() ([]Path, error) {
	prefix := p.key
	if !strings.HasSuffix(prefix, "/") {
		prefix += "/"
	}
	opt := swiftobject.ListOpts{
		Full: true,
		Path: prefix,
	}
	return p.readPath(opt)
}

// ReadTree implements Path::ReadTree.
func (p *SwiftPath) ReadTree() ([]Path, error) {
	prefix := p.key
	if !strings.HasSuffix(prefix, "/") {
		prefix += "/"
	}
	opt := swiftobject.ListOpts{
		Full:   true,
		Prefix: prefix,
	}
	return p.readPath(opt)
}

func (p *SwiftPath) Base() string {
	return path.Base(p.key)
}

func (p *SwiftPath) PreferredHash() (*hashing.Hash, error) {
	return p.Hash(hashing.HashAlgorithmMD5)
}

func (p *SwiftPath) Hash(a hashing.HashAlgorithm) (*hashing.Hash, error) {
	if a != hashing.HashAlgorithmMD5 {
		return nil, nil
	}

	md5 := p.hash
	if md5 == "" {
		return nil, nil
	}

	md5Bytes, err := hex.DecodeString(md5)
	if err != nil {
		return nil, fmt.Errorf("Etag was not a valid MD5 sum: %q", md5)
	}

	return &hashing.Hash{Algorithm: hashing.HashAlgorithmMD5, HashValue: md5Bytes}, nil
}

func isSwiftNotFound(err error) bool {
	if err == nil {
		return false
	}
	_, ok := err.(gophercloud.ErrDefault404)
	return ok
}
